[O] adjustment of schedules in org

[Christian Brandstätter]

Dear list,

I am rather new to org and I have a question to practitioners: How do 
you adjust your priorly set up dates (deadline extension, etc.)? I would 
manually delay certain entries. Thus I would lose the information of the 
original schedule. Is there a simple way to keep that information?
Or, differently: what would be a (more) reasonable way to go to adjust 
project time frames in emacs org?

Best,
Christian